Counterbalanced stair.



O. C. FOSSELMAN. GOUNTERBALANGED STAIR. APPLICATION FILED IEB.16, 1912.

Patented Nov. 11, 1913.

COLUMDM PLANOORAPH COH'WASHINGTDN. n. c.

o'r'ro o. EOSSELMAN, or Marv/001), ILLINOIS.-

COUNTERBALANGED i STAIR.

Specification of Letters latent.

Patented Nevin 1913.

'Application filed February 16,1912. Serial No; 678,093.

To all whom 26' may concern:

Be it known that I, OTTO. C. FossnL AN a citizen of the United States, residing at 'Maywood, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in -Counterbalanced "Stairs, of which the following is a full, clear,

concise,- and exact, description,- reference being 'had to r the accompanying drawings, forming .a; part of this specification.

.My invention relates to counterbalanced stairs such as are employed on the outside of buildings in 2 association .withfire-escapes,

-these stairs :cons'titutingthe last flights to the pavement. it is well known that counterbalanced stairs are employed for 1 these purposes in orderthat it may not normally .obstruct the streets or sidepassageways below-and aflfordineans for unauthorized access tothe buildings. There is usually a platform at thesecond floor of the bullding I and installation of rigid stairways'from this platform up to the top. The counterbalanced stair is mounted at thlsplatformand it lies. normally in a horizontal position away from the ground. Thestair is mounted upon a pivot and is counterbalanced by ,means of a weight. Because of the position of the platform and so as not to obstruct the passageway leading to the counterbalanced stair, it 1s practicalto place a coun- -terbalancing weight on' but one side of the I stair: and this is done ,byexten'ding the out- :side stringer rearwardly beyond the p vot rod. The-inside stringer stops at the p1vot rod. Then,- because the outside stringer is counterweighted and the inside stringer 1s not counterweighted, there 1s a tendency for the. forward end of the inside stringer to.

sag, due to gravit and this not only gives the fire-escape an unsightly appearance, but

-' the distortion due to this sagging causes an infirm structure when the stair is swung down to touch the ground. It is the ob ect of myanvention to provide meansfor overcoming this sagging effect, that is, for keeping the stringers in substantially parallel relation, and I do this by twisting the inside stringer before it is bolted to the treads extending between the stringers. This causes an initial distortion at the front of the fire-escape and the twist is in such a direction that the insidefon ward endof the fire-escape willb'e distorted upwardly and when the fire-escapeis hung fect-andl make these features the subject the efiect of gravity brings: the stringers into parallel relation.

in order to assist the torsional effect in the inside or unweighted stringer, T provide an auxiliary torsion ban; extending. along the, side thereof, and boltedtthereto in a manner =to augment the twist-(as -will be described presently. .I i also, provide novel .weight means for-secur1ng the counterbalancmg efmatter of'. some ofthe; appended claims.

invention is illustrated in .tl1e1accom- 1 panying drawings, in which Figure 1 is-a plan-view of.the counterbal anced stair as it is hung .upoii'tliepivot. member; Fig-'2 is-an end .tiew illustrating the .manner of twisting the uncounterweighted stringergfF g. 3 1s an endiview showing the -parts of; Fig. 2 assembled;-F-ig. a -1s an-elevational vlew of the sta1r-before.

. it is hungupon.the pivot; Fig-5 is a view 1 taken on the; plane of the line '.55 of- Fig.

1 and looking-in the direction indicatedby thearrows; Fig. .6 is a sectional view taken on the plane of the line -66 of Fig.4; and,

.Fig. 7 is a modified 'form of-uncounterwelghted. strlnger.

Like reference characters are applied to the same parts throughout the various figures.

Referring first to the, general form of my fire-escape, it will'be seen from Fig. 1 that the Wallet-a buildingisyshown at8 and that extending therefrom are-brackets 9 .which support a platform 10-and a pivot rod 11. Mounted upon the; pivot rod .11, by means of journal boxes 12 secured to the undersides thereof, aretheinside stringer l3. and the outside stringer-1 f which extend forwardlytogether; asshown and have se jcured between-them the plates 15, 15, pref erably constructed of a; plurality of rods set .in end pieces 16, 16. Railings 17,17 may be provided if desired. The outer stringer 14: is extended rearwardly beyond the pivot,

. rod 11 e a. considerable. distance and it is there provided with a countersweight 17 shown indetail inFigs. 1, 4t and 6. It will be seen that the stringer 14; is in the form of a channel beam and-that the weight 17 is in theform of two halves together one on each side of the stringer. Filler plates 18, 18 are providedland the bolts 19, 19-hold the parts together in properly assembled relation. .The-weight 17 is held. in the plates in any adjusted position by means of a set screw 20 and it will be seen that the weight can be adjusted longitudinally of the stringer. It is so disposed on the stringer that when the stringer is in a horizontal position the preponderance of the'weight will be at the rear; when, however, the stair is swung down, the center of gravity will be shifted, since the stringer is at a distance from the axis of the pivot member, so that the preponderance of 'weight will be on the forward part of the stair. The setscrew20 passes loosely through the parts of the weight, but is screw-threaded in a nut or plate 21 which is held stationary in a correspondingly shaped pocket in the weight, as shown in Fig. 4. It is evident that when the set-screw is tightened the entire weight will be firmly secured to the stringer. In some cases it is necessary to provide an auxiliary weight 22 and I make this weight of such form that it may fit within the channel iron and provide it with lugs 23, 23 which fit in correspondingly shaped depressions 21-, 2A on the inside of one of the weight parts. The forward end of this auxiliary weight is curved, as illustrated at 25, and it will appear that when it is desired to apply this auxiliary weight, the set screw 20 may be loosened so that the main weight 17 may be drawn back, the auxiliary weight being then inserted in the main weight so that the lugs in the former will fit in the depressions in the latter and the entire arrangement be then moved onto the stringer and secured in place. The curved or beveled forward edge of the auxiliary weight guides it properly into the channel iron. I provide this arrangement so that the parts may be standardized and so that the weight 17 may always be employed, the auxiliary weight being used only when necessary, as in the case of a slightly longer stair.

As illustrated in Fig. 2, in the course of construction of the fire-escape, the plates 15,15, by means of bolts 26, 26 passing through the end pieces 16 thereof, are secured to the channel iron forming the outside counterweighted stringer 14:. The uncounter-weighted stringer 13, however, is twisted in the direction of the arrow a so that in and of itself it will have the form illustrated in Fig. 2 and in Fig. 1 in dotted lines. That is, the forward end of the stringer is twisted about ninety degrees from the rearward end and the stringer then has the tendency to always assume this shape. hen the stringer 13 is turned back in order that the free ends of the plates may be bolted thereto, this tendency is resisted. The supremacy of the torsion in the stringer 13, however, throws down the plates 15, 15 and the result is that the inside forillustrated in Fig. 8. When the stair is hung upon the pivot member, the stringer 14- is held in a definite position by the counter-weight and, but for gravity, the end of the inside counter-weighted stringer would rise. Since the inside stringer is uncounterweighted, gravity acts to bring down the end of the inside stringer and, the twist originally being made to the proper extent, the stringers are then brought into substantially lateral alinement. In this way the sag is counter-acted and the stair may have the proper appearance and may also have the parts in proper mechanical arrangement.

It will be noted that in' Figs. 1 to 5 the inside uncounter-weighted stringer is shown as a twisted plate. In order that a plate of this kind may be increased in the amount of tension stored therein, if necessary, I provide a rod 27 extending lengthwise thereof and secured thereto as follows: The ends of the rod are widened as illustrated at 28, 28, forming arms in both directions, and one arm at one end is provided with a lug or extension 29 which engages the face of the plate. A bolt 30 passes through the opposite arm at that end and a bolt 31 passes through the diagonally opposite arm at the other end and when these bolts are tightened down the rod 27 will be twisted in a direction supplementing the twist of the stringer 13 itself. Quite the same result may be secured by using a channel iron 13 as illustrated in Fig. 7, in place of the flat stringer 13 since the edges of this iron add to its stability and secondly, the amount of torsion which may be stored therein.

I claim as new and desire to secure by Letters Patent:

1. A stair comprising stringers hung upon a horizontal pivot rod, a counterweight applied to but one of said stringers, the other of said stringers being twisted about its own axis, a torsion rod secured and confined to said last-named stringer and treads secured bet-ween said stringers.

2. A stair comprising stringers hung upon a horizontal pivot rod, a counterweight applied to but one of said stringers, the other of said stringers being twisted about its own axis, and treads secured between said stringers, the twist in the unweighted stringer tending to impel said counterweighted stringer downwardly.

3. A stair comprising stringers hung upon a horizontal pivot r'od, one of said stringers having an extension rearwardly beyond the pivot rod, a counterweight on said extension, the other of said stringers being twisted about its own axis, a torsion rod secured and confined to said last-named stringer and treads secured between said stringers, the twist in said unweighted stringer acting to maintain the stringers in substantial parallel relation.

4. A stair comprising stringers hung upon a horizontal pivot rod, a counterweight applied to but one of said stringers, and treads secured between the stringers, the normal position of the weighted stringer with the treads attached being planar and the normal position of the unweighted stringer being twisted or warped.

5. The process of alining the stringers in a counterbalanced stair in which but one stringer is counterweighted, which consists in twisting the unweighted stringer.

6. The process of alining the stringers in a counterbalanced stair in which but one stringer is counterweighted, which consists in securing the treads to the weighted stringer, twisting the unweighted stringer, and securing the treads to the twisted stringer.

In witness whereof, I hereunto subscribe my name this 8th day of February, A. D.,

OTTO G. FOSSELMAN. Witnesses:

ARTHUR H. BOETTOHER, ALBIN G. AHLBERG.

Copies of this patent ma; be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

